An active transsubstrate multichannel microelectrode (TMM) array is defined as an array of passive transsubstrate multichannel electrode sites with active electronic components (amplifiers and multiplexing circuitry) incorporated on the same Si substrate. An active TMM array is capable of simultaneously recording the neural activity of a population of cells. Separation between the active components and the passive electrode sites will be an outstanding feature. The interconnections between the front and back surfaces will be provided by conductive channels through Si substrate. The active components on the back surface are passivated by the thickness of the Si wafer itself without conventional passivation layers. The electrode surface is flat and there are no bonding wires on the front surface of the electrode. This yields an optimum contact between electrode and signal source. The transsubstrate channel must be very deep (about 250Mum), very narrow (about 10Mum in diameter), and separated by a minimum space (about 100Mum). The passive version produced must be well matched to the constraints imposed by the active components. Traditional integrated circuit fabrication techniques can not produce this kind of doping geometry. As a feasibility investigation to produce such as TMM array, laser-induced zone migration technique and anisotropic etching techniques (orientation dependent etching) will be employed. The potentially useful lasers will be investigated including a carbon dioxide laser, a carbon monoxide laser, and a Nd:YAG laser. The associated wavelengths should be near the absorption edge of Si. In parallel we will investigate an anisotropic etching technique and compare various Si orientations with respect to the aspect ratio (depth-to-width) as well as the surface state density in producing the TMM array. We will produce a 10x10 array of TMM elements incorporating preamplifiers and multiplexing circuitry into 10 recording channels. The long-term aim is to produce a 100x100 TMM array capable of simultaneously recording the neural activity of a population of cells.